Various packaging techniques have been used to build a load of unit products and subsequently wrap them for transportation, storage, containment and stabilization, protection and waterproofing. Products are often stacked as a load on a pallet to simplify handling of the products. The load is commonly wrapped with packaging material. One system uses wrapping machines to dispense and wrap packaging material around a load. Wrapping can be performed as an inline, automated packaging technique that dispenses and wraps packaging material around a load to cover and contain the load. Wrapping, whether accomplished by a turntable, rotating arm, vertical rotating ring, or horizontal rotating ring, typically covers the four vertical sides of the load with a film such as polyethylene film. In each of these arrangements, relative rotation is provided between the load and the packaging material dispenser to wrap packaging material about the sides of the load.
Wrapping machines provide relative rotation between a packaging material dispenser and a load either by driving the packaging material dispenser around a stationary load, or by rotating the load on a turntable. Upon relative rotation, packaging material is wrapped on the load. Ring style stretch wrappers generally include a roll of packaging material mounted in a dispenser that rotates about the load on a ring. Vertical rings move substantially vertically between an upper and lower position to wrap film around a load. In a vertical ring, as in turntable and rotating wrap arm apparatuses, the four vertical sides of the load are wrapped, along the height of the load.
When loads are wrapped, it is beneficial to wrap the film around the base of the load. If the load is on a pallet, it is beneficial to wrap the film around at least a top portion of the pallet supporting the load in order to secure the load to the pallet. The film exerts a containment force on the load, which may help to maintain the integrity of the load during transport. In other words, the film helps to keep the articles composing the wrapped load in the arrangement they are in immediately after being wrapped. If the containment force is insufficient, shifting of the load may occur during shipping. Shifting may lead to instability and/or damage to the load.
Containment force is the force exerted on the load by the packaging material wrapped around the load. Various devices and techniques have been used to measure the containment force exerted on a load by packaging material wrapped around the load. One such device that is Applicant's own work is illustrated in FIG. 10. The device includes a gauge that is coupled to a plate or disc. In order to use the device, a user makes a slit in the packaging material, and inserts the plate or disc through the slit so that the plate or disc is located between the packaging material and a surface of the load. The user holds a first end of a measuring device, such as a measuring tape, against the load surface, and then positions it so that it extends in a direction normal to the load surface. With the plate or disc and the measuring device in place, the user pulls the gauge outwardly in a direction normal to the surface of the load to a predetermined point along the measuring device. The reading on the gauge is indicative of the containment force. This device and technique had marginal success only, due to inaccuracy and difficulty of use. For example, the device could catch a gap between layers of packaging material, leading to inaccurate and unpredictable measurements. Furthermore, simultaneously pulling and holding the gauge, measuring the distance pulled, and reading the gauge, proved to be physically difficult for some users. Finally, it was not possible to obtain consistent results from one user to another.
Another device, also Applicant's own work, incorporates the use of a swiveling arm member that forms a “T” for engaging the packaging material. However, this device also has various drawbacks. For example, use of the device requires weakening the packaging material by cutting a relatively large horizontal slit in the packaging material to receive the swiveling arm, which is then rotated 90° into the position shown in FIG. 11. Furthermore, measurements obtained using this device proved to be inconsistent, and results were highly dependent upon operator technique. Additionally, the technique for using this device was slow and inefficient.
A subsequent device, also Applicant's own work, is illustrated in FIG. 12. The device includes two arms. A first arm engages a first side of the packaging material, and a second arm engages a second, opposite side of the packaging material. A base extends from the tops of the first and second arms, to which a gauge is attached. With the first and second arms in place and engaging the packaging material, a user pulls the gauge along a plane defined by the base. This device also suffers from drawbacks. For example, the device is limited to testing the packaging material at only the top or bottom of the load. Also, the exertion of a pulling force by the user at the top of the first and second arms causes distortion in the packaging material being tested. Furthermore, the device is only capable of taking relatively small vertical samples of the packaging material, and results tend to be inconsistent due to overlapped film variations.
The above-described devices for measuring containment force on wrapped loads suffer from flawed design, are difficult to use, cause substantial damage to the packaging material, and often times produce unreliable and inconsistent results. For these reasons, there is a need for containment force measuring device that can consistently produce fast, accurate, precise, and reliable results, while also being easy to use.
It is accordingly a primary object of the disclosure to provide a method and apparatus for measuring containment force on a wrapped load that can be used quickly and easily.
It is an additional object of the present disclosure to provide a method and apparatus for measuring containment force on a wrapped load with accuracy and precision.
It is an additional object of the present disclosure to provide a method and apparatus for measuring containment force on a wrapped load that is robust, and is capable of being used in any environment.
It is an additional object of the present disclosure to provide a method and apparatus for measuring containment force on a wrapped load that will cause minimal damage to the packaging material wrapped around the load.